This invention relates to the art of tools for performing work on a pipe and, more particularly, to a tool support for mounting a working tool on a pipe.
The present invention finds particular utility in connection with the mounting of a hole cutting tool on a pipe for drilling or cutting a hole therein and, accordingly, will be disclosed and discussed in detail in connection with such a tool. At the same time, it will be appreciated that the invention is applicable to the mounting of tools other than hole saws on a pipe upon which work is to be performed.
It is of course well known to provide a support for mounting a working tool such as a hole saw, drill or the like on a pipe through the use of a chain-type clamping arrangement in which a chain extends about the pipe between opposite ends of the support and is adjustable to releasably clamp the support on the pipe. Such supports heretofore available are shown, for example, in U.S. Pat. No. 2,281,366 to Metcalf and U.S. Pat. No. 2,585,343 to Newlon and are used in connection with a hole cutting tool available from the Ridge Tool Company of Elyria, Ohio under the latter's product designation Model HC-450. In these clamping arrangements, one end of the chain is anchored to an adjusting screw component and the other or free end of the chain is adapted to be adjustably interengaged with a holding component to allow the support to be mounted on pipes having different diameters. When the free end of the chain is interengaged with the holding component, the screw mechanism is rotated to tighten the chain about the pipe and thus clampingly engage the support thereon.
A major disadvantage of clamping arrangements of the foregoing character resides in the fact that it is difficult for a single worker to position the support and tool on a pipe and interengage the free end of the chain with the support to establish a preliminary mounted condition in which the operator can rotate the adjusting screw mechanism to tighten the chain and complete the mounting. In this respect, the operator must rest the support and tool on the pipe and stabilize the support and tool with one hand while using the other hand to move the free end of the chain under the pipe to the opposite side of the support and achieve interengagement of the free end of the chain with the holding component. If the pipe is of large diameter and/or at an elevation which requires the operator to stoop down or reach upwardly to manipulate the support, tool and chain, the difficulty of stabilizing the assembly with one hand and moving the chain with the other is optimized. In any event, engaging the free end of the chain with the holding component often must be achieved by "feel" as opposed to being able to observe relative displacement between the chain and holding component.
Another disadvantage with regard to such clamping chain arrangements is that the initial interengagement of the free end of the chain with the holding component results in the chain being loose to the extent that the operator must continue to stabilize the assembly with one hand until the chain is tightened through operation of the adjusting screw. In this respect, the holding component generally engages between adjacent chain rolls or roll pins extending from axially opposite sides of a link and the space between adjacent rolls or pins in the direction of the length of the chain is such that one roll or set of pins will not reach the holding component and the next adjacent ones that will result in the chain sagging away from engagement with the pipe. Accordingly, until the operator takes the slack out of the chain by rotating the adjusting screw, he or she must continue to stabilize the support and tool against displacement circumferentially of the pipe. Such support and tool assemblies are quite heavy and the difficulty with respect to stabilizing the assembly while rotating the adjusting screw increases as the diameter of the pipe decreases. Accordingly, it will be appreciated that considerable effort is required on the part of an operator to stabilize the support and tool when the assembly weighs more than 40 pounds and the diameter of the pipe can be as small as 11/4 inch as is possible in connection with use of the aforementioned Ridge Tool hole cutting tool.